(1) Field of the Invention
The present invention relates to a semiconductor memory device having an improved ground-potential supplying system for memory cells having capacitors and for peripheral units of the memory cells.
(2) Description of the Prior Art
In general, dynamic semiconductor memory devices comprise a plurality of memory cells, each having one transistor and one capacitor connected in series between a bit line and a power supply line. The capacitor is used to store data and has two electrodes opposite to each other, one connected to the transistor and the other connected to a power supply line. Hereinafter, the electrode of the capacitor connected to the transistor is referred to as a "storage electrode", and the electrode opposite the storage electrode is referred to as an "opposite electrode". Usually, the power supply line connected to the opposite electrode of the capacitor is supplied with a voltage of, for example, 5 V, for the operation of peripheral circuits of the memory cells. This operating voltage, however easily fluctuates under the influence of external circuits. This fluctuation causes a potential fluctuation at the storage electrode of the capacitor, resulting in a possible error operation of the sense amplifier for detecting small potential differences between bit lines.
To avoid such an error operation, recent technology has replaced the use of the power supply line with a ground-potential supplying line (hereinafter simply referred to as a "ground line") connected to the opposite electrode of the capacitor. This is because the voltage fluctuation of a ground line is less than the voltage fluctuation of a power supply line. However, when the peripheral circuits operate, a current flows through the ground line, whereby the resistance of the line causes fluctuation of the potential at each point on the line. Therefore, the potential at the opposite electrode of the capacitor fluctuates even when a ground line is connected to the opposite electrode of the capacitor. Recent technology has consequently still not solved the above-mentioned problems.